1. Field of the Invention
Illustrative aspects of the present invention relate to an image reader that reads an image using a close-contact-type image sensor.
2. Description of the Related Art
Conventionally, as an image reader, which is mounted on a facsimile, a copying machine or the like, an image reader which uses a close-contact-type image sensor (CIS: Contact Image Sensor) is known.
The CIS is advantageous compared with an image sensor of a charge Coupled Devices (CCD) method with respect to a point that the CIS can be largely miniaturized and can largely reduce a weight thereof. On the other hand, compared with the image sensor of the CCD method, the CIS has a drawback that a focusing depth is extremely shallow and a range in which an image can be clearly read is narrow. For example, when a focusing point of the CIS is positioned on an upper surface of the platen glass and a document is placed on a surface of the platen glass, an image of a document which is printed on a portion slightly floated from the surface of the platen glass is read blurred out of focus. Accordingly, at the time of shipment from a factory, although it is possible to perform the clear reading over the whole document with respect to non-wrinkled document when the adjustment is made to position the focusing point of the CIS on an upper surface of the platen glass, when an image is read from a book in a spread state or an image is read from a wrinkled document, an image which is read at a portion floated from the surface of the platen glass becomes obscure.
Further, since the focusing depth is extremely shallow as described above, when the image readers are produced in a mass production basis by uniformly setting a distance between the platen glass and the CIS, due to the irregularities in size or the like between the CIS and other parts, there exists a possibility of manufacturing an image reader in which the focusing point of the CIS is not positioned above the upper surface of the platen glass.
Accordingly, in a plant which manufactures image readers using the CIS, with respect to each one of the image reader to be manufactured, the distance between the platen glass and the CIS (hereinafter referred to as “glass-CIS distance”) is adjusted using spacers which differ in thickness or screw height adjusting screws (for example, see J-P-A-2005-167817) so as to position a focusing point of the CIS on an upper surface of the platen glass. That is, the adjustment of the distance between the platen glass and the CIS using the spacers or the height adjusting screws is performed manually.